Bonsoir
Développer
R= (2x-7) (4-3x) -2x²
E = 8x - 6x² - 28 + 21x - 2x²
E = - 6x² - 2x² + 8x + 21x - 28
E = - 8x² + 29x - 28
S = (7x+3)² - (4x-5)²
S = 49x² + 42x + 9 - (16x²- 40x + 25)
S = 49x²+ 42x + 9 - 16x² + 40x - 25
S = 49x² - 16x² + 42x + 40x + 9 - 25
S = 33x² + 82x - 16
T = (4x-8)(4x+8) -2x(x+2)
T = 16x² - 64 - 2x² - 4x
T = 16x² - 2x² - 4x - 64
T = 14x² - 4x - 64
Factoriser
9x² - 31 --> Erreur d'expression tu as peut-être voulu écrire :
9x² - 81 = (3x - 9) (3x + 9)
A = 81 - 4t² = (9 - 2t) (9 + 2t)
B = ( -5x+3) (2x-7) - ( 4x-1)(-5x+3)
B= (- 5x + 3) [(4x - 1) - (2x - 7)]
B = (- 5x + 3) (4x - 1 - 2x + 7)
B = (- 5x + 3) (2x + 6)
B = 2 (x + 3) (- 5x + 3)
C=( 8x-9)² - (3x+5)² = (8x - 9 - 3x - 5) (8x - 9 + 3x + 5) = (5x - 14) (11x - 4)
Résoudre l'équation B=0
B = 0
2 (x + 3) (- 5x + 3) = 0
x + 3 = 0 ou - 5x + 3 = 0
x = - 3 - 5x = - 3
x = 3/5.